The former 110m gold medallist, in his first major interview since his spectacular exit in London, told state broadcaster CCTV he "felt healthy standing on the starting line".

Liu also said he would not take part in the next Olympics. The comments were given as reports circulated that CCTV knew in advance that Liu was injured, but were banned from releasing the information by China's propaganda department.

According to reports quoted by Hong Kong's South China Morning Post, broadcaster Yang Jian, who wept live on air, had prepared scripts in advance in case Liu limped out for the second Games running.

Liu's latest injury, markedly similar to his withdrawal in 2008, caused widespread shock in China. A specially created tribute website quickly drew 28 million messages of support.

"Standing on the line, I felt I was a healthy Liu Xiang. Actually I was having problems on my foot at the time, but I felt I could run fast," Liu told CCTV, in the interview aired late on Thursday.

"(But) when I tried the first hurdle, I felt like I was lashed by a whip."

In scenes strongly reminiscent of Beijing 2008 - when a broadcaster also dissolved into tears - the 2004 champion crashed into the first hurdle in his heat as his right Achilles tendon gave way.

After being helped up, he hopped the length of the course, kissed the last hurdle and was embraced by fellow competitors in one of the enduring images of the London Games.

Liu, 29, underwent surgery in London before returning to China, with his future career in serious doubt.

But allegations of a plot to hush up Liu's injury began circulating on Thursday, and were among the most talked about topics on Sina Weibo, a microblogging service similar to Twitter, which is banned in China.

"CCTV and Liu Xiang put on a show to trick the world," posted one user. "For CCTV, tricking the people is the easiest choice," wrote another.

Coach Feng Shuyong had admitted in the run-up to London that Liu, China's first male Olympic athletics champion, was troubled by injury.

A senior editor of CCTV's Olympics team told the South China Morning Post that Liu was believed to have suffered a flare-up in training, and was advised by a medical expert that the injury was severe.

"Instructions were circulated among our colleagues saying it should be considered a victory as long as Liu showed up to the starting line," said the editor, who was quoted anonymously.

CCTV declined to comment on the reports, the latest in a line of cover-up rumours in China in recent weeks.

These include the suggestion that Gu Kailai, wife of disgraced politician Bo Xilai, used a stand-in for her recent high-profile murder trial, after TV footage showed her standing in the dock looking plumper than usual.

Chinese web users have also questioned the authenticity of images broadcast on CCTV showing the corpse of Zhou Kehua, a multiple murder suspect who was shot dead last week by police after a widely publicised manhunt.

At the Beijing Olympics, organisers admitted broadcasting computer-generated fireworks during the opening ceremony, and that an angelic nine-year-old soloist lip-synched to a recording by another girl who was dumped for her inferior looks.